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USGS2019

Whooping Cranes past and present

The Whooping Crane ( Grus americana ), endemic to North America, is the rarest of all crane species. It is believed that in the early 1800s, the Whooping Crane was widespread in North America, though it was never very abundant. Whooping Crane numbers decreased precipitously as westward migration of Euro-American settlers converted prairie to cropland and the birds were hunted. By the early 1940s the total population was as low as 21 individuals; the migratory Aransas-Wood Buffalo Population, from which all extant Whooping Cranes are descended, dwindled to 16 in 1941. The threat of extinction was very real. These dire circumstances excited the interest of ornithologists and conservationists in the United States and Canada, and much has been accomplished since to conserve the species. To describe the historical and ongoing conservation activities for Whooping Cranes, we distinguish two eras of Whooping Crane Conservation: before 1950 and after 1950. The first era was characterized by publicizing the plight of the Whooping Crane and halting hunting and habitat destruction. The second era, continuing to the present, has been characterized by development of information about cranes through scientific study, conservation efforts of governmental and nongovernmental organizations, protection of the species under the Endangered Species Act in the United States and the Species at Risk Act in Canada, habitat protection, and reintroduction of new populations of Whooping Cranes. Publication of the monograph, The Whooping Crane by Robert Porter Allen, in 1952 stimulated much of the work of the second era, and still stands as the definitive work on the biology of Whooping Cranes. The remnant Aransas Wood Buffalo Population, which is crucial to species recovery, has grown to over 430 birds as of winter 2016–17. Four reintroduced populations were started in the second era; two are currently active efforts (the Eastern Migratory population and the Louisiana Nonmigratory Population), although neither population is selfsustaining. This volume gathers together the current scientific information about Whooping Cranes and the experiences of various reintroduction and management operations, to provide a baseline from which a third era of Whooping Crane conservation may be launched.

Book chapter↗

USGS2014

Radiocarbon dating loess deposits in the Mississippi Valley using terrestrial gastropod shells (Polygyridae, Helicinidae, and Discidae)

Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that are accurate to within a few hundred years. In contrast, shells of the genus Mesodon ( Mesodon elevatus and Mesodon zaletus ) contain significant and variable amounts of old carbon, yielding ages that are up to a couple thousand 14 C years too old. Although terrestrial gastropod shells have tremendous potential for 14 C dating loess deposits throughout North America, we acknowledge that accuracy to within a few hundred years may not be sufficient for those interested in developing high-resolution loess chronologies. Even with this limitation, however, 14 C dating of terrestrial gastropod shells present in Mississippi Valley loess deposits may prove useful for researchers interested in processes that took place over multi-millennial timescales or in differentiating stratigraphic units that have significantly different ages but similar physical and geochemical properties. The results presented here may also be useful to researchers studying loess deposits outside North America that contain similar gastropod taxa..

Mississippi Valley↗

USGS2016

Geochemical evidence for seasonal controls on the transportation of Holocene loess, Matanuska Valley, southern Alaska, USA

Loess is a widespread Quaternary deposit in Alaska and loess accretion occurs today in some regions, such as the Matanuska Valley. The source of loess in the Matanuska Valley has been debated for more than seven decades, with the Knik River and the Matanuska River, both to the east, being the leading candidates and the Susitna River, to the west, as a less favorable source. We report here new stratigraphic, mineralogic, and geochemical data that test the competing hypotheses of these river sources. Loess thickness data are consistent with previous studies that show that a source or sources lay to the east, which rules out the Susitna River as a source. Knik and Matanuska River silts can be distinguished using Sc–Th–La, La N /Yb N vs. Eu/Eu ∗ , Cr/Sc, and As/Sb. Matanuska Valley loess falls clearly within the range of values for these ratios found in Matanuska River silt. Dust storms from the Matanuska River are most common in autumn, when river discharge is at a minimum and silt-rich point bars are exposed, wind speed from the north is beginning to increase after a low-velocity period in summer, snow depth is still minimal, and soil temperatures are still above freezing. Thus, seasonal changes in climate and hydrology emerge as critical factors in the timing of aeolian silt transport in southern Alaska. These findings could be applicable to understanding seasonal controls on Pleistocene loess accretion in Europe, New Zealand, South America, and elsewhere in North America.

Alaska↗

USGS2009

Pilot studies for the North American Soil Geochemical Landscapes Project - Site selection, sampling protocols, analytical methods, and quality control protocols

In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada sampled and chemically analyzed soils along two transects across Canada and the USA in preparation for a planned soil geochemical survey of North America. This effort was a pilot study to test and refine sampling protocols, analytical methods, quality control protocols, and field logistics for the continental survey. A total of 220 sample sites were selected at approximately 40-km intervals along the two transects. The ideal sampling protocol at each site called for a sample from a depth of 0-5 cm and a composite of each of the O, A, and C horizons. The <2-mm fraction of each sample was analyzed for Al, Ca, Fe, K, Mg, Na, S, Ti, Ag, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Ga, In, La, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Sn, Sr, Te, Th, Tl, U, V, W, Y, and Zn by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry following a near-total digestion in a mixture of HCl, HNO 3 , HClO 4 , and HF. Separate methods were used for Hg, Se, total C, and carbonate-C on this same size fraction. Only Ag, In, and Te had a large percentage of concentrations below the detection limit. Quality control (QC) of the analyses was monitored at three levels: the laboratory performing the analysis, the USGS QC officer, and the principal investigator for the study. This level of review resulted in an average of one QC sample for every 20 field samples, which proved to be minimally adequate for such a large-scale survey. Additional QC samples should be added to monitor within-batch quality to the extent that no more than 10 samples are analyzed between a QC sample. Only Cr (77%), Y (82%), and Sb (80%) fell outside the acceptable limits of accuracy (% recovery between 85 and 115%) because of likely residence in mineral phases resistant to the acid digestion. A separate sample of 0-5-cm material was collected at each site for determination of organic compounds. A subset of 73 of these samples was analyzed for a suite of 19 organochlorine pesticides by gas chromatography. Only three of these samples had detectable pesticide concentrations. A separate sample of A-horizon soil was collected for microbial characterization by phospholipid fatty acid analysis (PLFA), soil enzyme assays, and determination of selected human and agricultural pathogens. Collection, preservation and analysis of samples for both organic compounds and microbial characterization add a great degree of complication to the sampling and preservation protocols and a significant increase to the cost for a continental-scale survey. Both these issues must be considered carefully prior to adopting these parameters as part of the soil geochemical survey of North America.

Applied Geochemistry↗

USGS2009

Application of in vitro extraction studies to evaluate element bioaccessibility in soils from a transect across the United States and Canada

In vitro bioaccessibility tests (IVBA) are inexpensive, physiologically-based extraction tests designed to estimate the bioaccessibility of elements along ingestion exposure pathways. Published IVBA protocols call for the testing to be done on the <250-??m fraction of soil, as these particles are most likely to adhere to the hands of children and be ingested. Most IVBA in the literature to date have been applied to soil samples from highly contaminated sites or to spiked samples, and relatively little work has been done to evaluate bioaccessibility of elements in a wide variety of uncontaminated 'background' soils. In 2004, the US Geological Survey and the Geological Survey of Canada sampled soils along north-south and east-west transects across the two countries to test and refine sampling and analytical protocols recommended for the planned soil geochemical survey of North America. Samples were collected at 220 sites selected randomly at approximately 40-km intervals. The focus of the investigation presented in this paper was twofold: (1) to begin to examine variations in bioaccessibility of As, Cd, Cr, Ni and Pb in a number of 'background' (i.e., unpolluted) soils from around North America and (2) to determine if there are significant differences that would preclude using the standard size fraction of <2 mm for extraction with a simulated gastric fluid as an expeditious and inexpensive bioaccessibility screening tool for the large numbers of future samples to be collected by this continental-scale project. A subset of 20 soil samples collected along the north-south transect at a depth of 0-5 cm was used for this study. Two separate size fractions (<2 mm and <250 ??m) were extracted using a simulated human gastric fluid consisting of a solution of HCl and glycine adjusted to a pH of 1.5. In general, the leachate results for the <2-mm size fraction were not substantially different than those for the <250-??m size fraction for concentrations of As, Cd, Cr, Ni and Pb. Leachate concentrations for Cd, Ni and Pb appear to be controlled to some extent by the total concentration of the element in soil. Bioaccessibility of the elements in this study decreased in the order, Cd > Pb > Ni > As > Cr.

Applied Geochemistry↗

USGS2023

Genetic analysis of North American Phragmites australis guides management approaches

Phragmites australis subsp. australis is an invasive and ecologically detrimental plant in multiple regions of North America. Its co-occurrence with the native subspecies, and multiple instances of hybridization, has created the need to differentiate Phragmites subspecies or haplotypes so that management can be appropriately targeted to the invader. We compiled a review of current genetic discrimination methods among the three Phragmites subspecies inhabiting the United States and Canada, and discussed how each method can contribute to control of the introduced subspecies while preserving the two endemic subspecies. We also discussed various control tools and the implications of Phragmites genetics for implementation. The Phragmites subspecies endemic to North America have environmental or infrastructure significance (e.g., habitat sustainability, biodiversity, storm surge and erosion protection). Thus, faster and more accurate differentiation among the endemic and introduced subspecies is needed. Additionally, more in-depth genetic information on Phragmites subspecies could support better management decisions, as well as the development of improved control treatments. This review highlights technologies and approaches currently available for genetic identification, recently collected genomic, transcriptomic and proteomic information, and implications for biological control and herbicide treatments.

Aquatic Botany↗

USGS2016

Experimental infection of six North American fish species with the North Carolina strain of spring Viremia of Carp Virus

Spring viremia of carp virus (SVCV) is a rhabdoviral pathogen associated with disease outbreaks in cultured and wild fish worldwide. Common carp ( Cyprinus carpio carp ), and koi ( C. carpio koi ) suffer the highest mortalities from SVCV infections, while other cyprinid fish species have varying susceptibility. Although salmonid fish typically are considered refractory to infection by SVCV, there have been a few reports suggesting infection has occurred in rainbow trout ( Oncorhynchus mykiss ). There have been no reports of Percid fish being infected with SVCV. Since the first North American outbreak of SVCV at a North Carolina koi farm in 2002 there have been eight subsequent detections or outbreaks of SVCV among fish species from the families of Cyprinidae and Centrarchidae within the US and Canada. Thus, this exotic virus is considered a potential threat to native and cultured fish populations in North America. We performed multiple experimental challenges with fish species from three families ( Salmonidae , Cyprinidae , and Percidae ) to identify the potential risk associated with SVCV exposure of resident fish populations in North America. Three salmonid species, rainbow and steelhead trout ( Oncorhynchus mykiss ), Chinook salmon ( O. tshawytscha ), and sockeye salmon ( O. nerka ), were challenged by immersion or injection with the North Carolina SVCV isolate. Two cyprinid species, koi and fathead minnow ( Pimephales promelas ) and one percid species, yellow perch ( Perca flavescens ) were also challenged. Koi were highly susceptible to SVCV up to 11 months of age and fathead minnows had chronic disease expression with moderate mortality (29%). SVCV also induced moderate mortalities (33%) in yellow perch fry. Virus challenged salmonid fish had cumulative percent mortalities ranging from 0 to 100%, with sockeye salmon fry being the most vulnerable. A sub-sample of mortalities and survivors were screened for virus by plaque assay and reverse transcription polymerase chain reaction. In general, all mortalities tested positive for SVCV with high viral titers while survivors had variable persistence of SVCV with overall lower virus titers. Our SVCV challenges of multiple North American fish species suggested that host age is a key factor in determining disease outcome. Other factors, such as fish broodstock, virus strain, water temperature, and rearing conditions in association with the intrinsic level of species susceptibility may also impact infection dynamics. This is the first report of SVCV infecting a species (yellow perch) in the family Percidae and that sockeye salmon fry can suffer similarly high mortalities as the primary SVCV host species.

Aquaculture↗

USGS2016

Acid rain and its environmental effects: Recent scientific advances

The term ‘acid rain’ refers to atmospheric deposition of acidic constituents that impact the earth as rain, snow, particulates, gases, and vapor. Acid rain was first recognized by Ducros (1845) and subsequently described by the English chemist Robert Angus Smith (Smith, 1852) whose pioneering studies linked the sources to industrial emissions and included early observations of deleterious environmental effects (Smith, 1872). Smith's work was largely forgotten until the mid-20th century when observations began to link air pollution to the deposition of atmospheric sulfate (SO 4 2− ) and other chemical constituents, first near the metal smelter at Sudbury, Ontario, Canada, and later at locations in Europe, North America, and Australia (Gorham, 1961). Our modern understanding of acid rain as an environmental problem caused largely by regional emissions of sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) stems from observations in the 1960s and early 1970s in Sweden by Svante Odén (Odén, 1976), and in North America by Gene Likens and colleagues (Likens and Bormann, 1974). These scientists and many who followed showed the link to emissions from coal-fired power plants and other industrial sources, and documented the environmental effects of acid rain such as the acidification of surface waters and toxic effects on vegetation, fish, and other biota.

Atmospheric Environment↗

USGS2021

Evaluation of regulatory action and surveillance as preventive risk-mitigation to an emerging global amphibian pathogen Batrachochytrium salamandrivorans (Bsal)

The emerging amphibian pathogen Batrachochytrium salamandrivorans (Bsal) is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort. Risk-based approaches to decision-making can extend to adaptive management cycles by periodically incorporating new information that reduces uncertainty in an estimate of risk or to assess the effect of mitigation actions which reduce risk directly. Our objectives were to evaluate the effects of regulatory action on the introduction of Bsal to the U.S., quantify how a large-scale surveillance effort impacted consequence risk, and to combine other new information on species susceptibility to re-evaluate Bsal risk to the U.S. Import regulations effectively reduced import volume of targeted species, but new research on species susceptibility suggests the list of regulated species was incomplete regarding Bsal reservoir species. Not detecting Bsal in an intensive surveillance effort improved confidence that Bsal was not present, however, the overall risk-reduction impact was limited because of the expansive area of interest (conterminous United States) and limited time frame of sampling. Overall, the preventive actions in response to the Bsal threat did reduce Bsal risk in the U.S. and we present an updated risk assessment to provide information for adaptive decision-making.

Biological Conservation↗

USGS2005

Base- and precious-metal deposits in the Basin and Range of Southern California and Southern Nevada - Metallogenic implications of lead isotope studies

Southern California and southern Nevada contain abundant lead-zinc deposits with strikingly different characteristics. On the west, the Darwin Terrane contains abundant Jurassic and Cretaceous intrusions surrounded by lead-zinc skarn and replacement deposits rich in pyrite and manganese minerals. The Tecopa Terrane is east of the Darwin Terrane and contains some lead deposits that are hosted by the Proterozoic Noonday Dolomite. These lead deposits have no consistent relation to igneous rocks; they contain mainly galena, and are devoid of pyrite and manganese minerals. Other skarn and vein deposits in the Ivanpah and Tecopa districts are more closely associated with igneous rocks. Mississippi Valley type lead-zinc deposits are present still farther to the east in the Goodsprings Terrane in Nevada. These deposits are hosted by breccias formed below the Mississippian-Pennsylvanian unconformity and are unrelated to igneous rocks. Deposits in the Darwin Terrane have lead isotopic signatures that lie along a mantle-sediment mixing line indicating that they formed in a continental arc setting analogous to that for the plutons in the Sierra Nevada batholith [Chen, J.H. and Tilton, G.R., 1991. Application of lead and strontium isotopic relationships to the petrogenesis of granitoid rocks, central Sierra Nevada batholith, California. Geological Society of America Bulletin 103, 439-447]. Encroachment of this continental arc on the North American continent in the eastern part of the Darwin Terrane resulted in a lead isotopic signature that is like that of the strongly contaminated plutons [Chen, J.H. and Tilton, G.R., 1991. Application of lead and strontium isotopic relationships to the petrogenesis of granitoid rocks, central Sierra Nevada batholith, California. Geological Society of America Bulletin 103, 439-447]. Many deposits from the Inyo Mountains on east side of the Owens Valley have lead isotopic signatures that reflect this encroachment. To the east in the Tecopa Terrane, encroachment of the continental arc on the Mojave crust resulted in partial melting of 1.7 Ga amphibolite and granulite facies rocks to produce the plutons and mineral deposits associated with plutons in this terrane. Lead from deposits in this terrane hosted in the Proterozoic Noonday Dolomite and associated rocks have a lead isotope signature that reflects hydrothermal circulation of fluids in the Mojave supracrustal rocks. The boundary between the Darwin Terrane and the Tecopa Terrane lies just west of the Ash Valley-Panamint Range Fault and is bounded by the Towne Fault on the north and the Garlock Fault on the south. Lead isotopic data from the Goodsprings district in southwestern Nevada, east of the Tecopa Terrane, form a 1.45 Ga linear array that is indicative of Mississippi Valley type mineralization. Although we have no independent evidence of the timing of the tectonic events that formed these deposits, it is likely that all formed as a result of the Mesozoic collision of the Panthalassen crust with the North American continent. ?? 2005 Elsevier B.V. All rights reserved.

Earth-Science Reviews↗

USGS2024

Palaeontological signatures of the Anthropocene are distinct from those of previous epochs

The “Great Acceleration” beginning in the mid-20th century provides the causal mechanism of the Anthropocene, which has been proposed as a new epoch of geological time beginning in 1952 CE. Here we identify key parameters and their diagnostic palaeontological signals of the Anthropocene, including the rapid breakdown of discrete biogeographical ranges for marine and terrestrial species, rapid changes to ecologies resulting from climate change and ecological degradation, the spread of exotic foodstuffs beyond their ecological range, and the accumulation of reconfigured forest materials such as medium density fibreboard (MDF) all being symptoms of the Great Acceleration. We show: 1) how Anthropocene successions in North America, South America, Africa, Oceania, Europe, and Asia can be correlated using palaeontological signatures of highly invasive species and changes to ecologies that demonstrate the growing interconnectivity of human systems; 2) how the unique depositional settings of landfills may concentrate the remains of organisms far beyond their geographical range of environmental tolerance; and 3) how a range of settings may preserve a long-lived, unique palaeontological record within post-mid-20th century deposits. Collectively these changes provide a global palaeontological signature that is distinct from all past records of deep-time biotic change, including those of the Holocene.

Earth Science Reviews↗

USGS2025

Modeling current and future distribution of invasive tegu lizards along geopolitical boundaries in the contiguous United States: Implications for invasion threat

Historically, constrained temperature ranges limited the spread of invasive herpetofauna into temperate climates, but climate change is predicted to facilitate broader distributions. There are three species of tegu lizards native to South America and available in the pet trade that have a high risk of invasion and deleterious impacts to native ecosystems in the United States (US). There are four populations of the black and white tegu ( Salvator merianae ) in Florida and sightings as far north as North Carolina and west as California. Red tegus ( S. rufescens ) have been observed in Florida, and there is an established population of gold tegus ( Tupinambis teguixin ) in Florida. We updated previous distribution models for the contiguous United States (CONUS) that used occurrence points from their native range in South America to evaluate potential changes given current and future climate scenarios (+2 °C and +4 °C warming). Under current climate conditions, one or more tegu species have the potential to occupy most ecoregions in the CONUS. Under a + 4 °C warming scenario, suitable habitat increases by 11 % for S. merianae , 31 % for S. rufescens . The proportion of suitable habitat for T. teguixin was small under all scenarios, but increased from 0.0003 to 0.0017. For S. merianae , parts of Florida become less suitable, while suitability increases in this region for the other two species. Additionally, much of the western US is projected to be suitable for S. rufescens . Our case study underscores the potential for climate change to compound invasion threats that could outpace effective managerial responses.

contiguous United States↗

USGS2014

Structure and tectonics of the northwestern United States from EarthScope USArray magnetotelluric data

The magnetotelluric component of the EarthScope USArray program has covered over 35% of the continental United States. Resistivity tomography models derived from these data image lithospheric structure and provide constraints on the distribution of fluids and melt within the lithosphere. We present a three-dimensional resistivity model of the northwestern United States which provides new insight into the tectonic assembly of western North America from the Archean to present. Comparison with seismic tomography models reveals regions of correlated and anti-correlated resistivity and velocity that help identify thermal and compositional variations within the lithosphere. Recent (Neogene) tectonic features reflected in the model include the subducting Juan de Fuca–Gorda plate which can be traced beneath the forearc to more than 100 km depth, high lithospheric conductivity along the Snake River Plain, and pronounced lower-crustal and upper-mantle conductivity beneath the Basin and Range. The latter is abruptly terminated to the northwest by the Klamath–Blue Mountains Lineament, which we interpret as an important structure during and since the Mesozoic assembly of the region. This boundary is interpreted to separate hot extended lithosphere from colder, less extended lithosphere. The western edge of Proterozoic North America, as indicated by the Cretaceous initial 87 Sr/ 86 Sr = 0.706 contour, is clearly reflected in the resistivity model. We further image an Archean crustal block (“Pend Oreille block”) straddling the Washington/Idaho border, which we speculate separated from the Archean Medicine Hat block in the Proterozoic. Finally, in the modern Cascades forearc, the geometry and internal structure of the Eocene Siletz terrane is reflected in the resistivity model. The apparent eastern edge of the Siletz terrane under the Cascades arc suggests that pre-Tertiary rocks fill the Washington and Oregon back-arc.

Earth and Planetary Science Letters↗

USGS2019

The missing dead: The lost role of animal remains in nutrient cycling in North American Rivers

While leaf litter, wood, and other plant remnants are known to play a central role in lotic ecosystems, animal remains (carcasses, bones, shells) have received less attention. We propose a simple classification scheme for animal remains in rivers based on origin (authochthonous vs. allochthonous) and frequency (pulsed vs continuous). We then present case studies in which we estimate the former biomass of several taxonomic groups that are now diminished in abundance to determine whether their remains could have historically constituted a significant flux of nutrients in rivers of North America. We focus on bones and shells, which decompose slowly and could provide long-term reservoirs of nutrients. We find that carcasses of alligator snapping turtles, once abundant in southeastern rivers, could have provided an amount of phosphorus equivalent to about 1% of total phosphorus (TP) load at median flow, and more at low flows. Mussel shells could have contributed a similar amount (0.8% of TP) but the contribution of beaver carcasses, even at former abundances, was likely small. In contrast, a single documented mass drowning of bison in the Assiniboine River could have contributed half the annual TP load for that river. Such drownings could have been a common occurrence prior to the loss of most wild terrestrial megafauna in North America. We conclude that animal remnants, particularly allochthonous remains from terrestrial animals, formerly played a substantial role in nutrient cycling. Existing models of ecosystem function under reference conditions are incomplete without consideration of these lost animal legacies.

Food Webs↗

USGS2013

Effect of long-term understory prescribed burning on standing and down dead woody material in dry upland oak forests

Dead woody material, long ignored or viewed as a nuisance for forest management, has gained appreciation for its many roles in the forest including wildlife habitat, nutrient storage and cycling, energy for trophic webs, protection of soil, fuel for fire and carbon storage. The growing interest in managing dead woody material has created strong demand for greater understanding of factors controlling amounts and turnover. Prescribed burning, an important management tool, may have strong effects of dead woody material given fire’s capacity to create and consume dead woody material. We determined effects of long-term understory prescribed burning on standing and down woody material in upland oak forests in south-central North America. We hypothesized that as frequency of fire increased in these stands the amount of deadwood would decrease and the fine woody material would decrease more rapidly than coarse woody material. The study was conducted in forests dominated by post oak ( Quercus stellata ) and blackjack oak ( Quercus marilandica ) in wildlife management areas where understory prescribed burning had been practiced for over 20 years and the range of burn frequencies was 0 (unburned) fires per decade (FPD) to 4.6 FPD. The amount of deadwood was low compared with more productive forests in southeastern North America. The biomass (24.7 Mg ha -1 ) and carbon stocks (11.7 Mg ha -1 ) were distributed among standing dead (22%), coarse woody debris (CWD, dia. > 7.5 cm., 12%), fine woody debris (FWD, dia. < 7.5 cm., 23%), and forest floor (43%). There was no evidence that understory prescribed burning influenced the amount and size distribution of standing and down dead woody material. There were two explanations for the lack of a detectable effect. First, a high incidence of severe weather including ice storms and strong winds that produce large amounts of deadwood intermittently in an irregular pattern across the landscape may preclude detecting a strong effect of understory prescribed burning. Second, fire suppression during the first one-half of the 20th Century may have led to encroachment of woody plants into forest gaps and savannas creating a patchwork of young and old stands that produced deadwood of different sizes and at different rates.

Forest Ecology and Management↗

USGS2016

Spatial and temporal trends of drought effects in a heterogeneous semi-arid forest ecosystem

Drought has long been recognized as a driving mechanism in the forests of western North America and drought-induced mortality has been documented across genera in recent years. Given the frequency of these events are expected to increase in the future, understanding patterns of mortality and plant response to severe drought is important to resource managers. Drought can affect the functional, physiological, structural, and demographic properties of forest ecosystems. Remote sensing studies have documented changes in forest properties due to direct and indirect effects of drought; however, few studies have addressed this at local scales needed to characterize highly heterogeneous ecosystems in the forest-shrubland ecotone. We analyzed a 22-year Landsat time series (1985–2012) to determine changes in forest in an area that experienced a relatively dry decade punctuated by two years of extreme drought. We assessed the relationship between several vegetation indices and field measured characteristics (e.g. plant area index and canopy gap fraction) and applied these indices to trend analysis to uncover the location, direction and timing of change. Finally, we assessed the interaction of climate and topography by forest functional type. The Normalized Difference Moisture Index (NDMI), a measure of canopy water content, had the strongest correlation with short-term field measures of plant area index ( R 2 = 0.64) and canopy gap fraction ( R 2 = 0.65). Over the entire time period, 25% of the forested area experienced a significant ( p -value < 0.05) negative trend in NDMI, compared to less than 10% in a positive trend. Coniferous forests were more likely to be associated with a negative NDMI trend than deciduous forest. Forests on southern aspects were least likely to exhibit a negative trend while north aspects were most prevalent. Field plots with a negative trend had a lower live density, and higher amounts of standing dead and down trees compared to plots with no trend. Our analysis identifies spatially explicit patterns of long-term trends anchored with ground based evidence to highlight areas of forest that are resistant, persistent or vulnerable to severe drought. The results provide a long-term perspective for the resource management of this area and can be applied to similar ecosystems throughout western North America.

Colorado, Utah, Wyoming↗

USGS2019

Patterns of acoustical activity of bats prior to and 10 years after WNS on Fort Drum Army Installation, New York

Previous acoustic surveys, netting, and count data have shown that overall bat activity patterns have shifted among most species between pre- and post-white-nose syndrome (WNS) years in much of North America where WNS has occurred. However, the significance of these changes is based on the species-specific susceptibility to WNS. We used acoustically recorded echolocation passes obtained at Fort Drum, New York to describe changes in bat activity pre-WNS (2004–2007) to post-WNS (2008–2018). We examined seasonal and yearly changes in bat activity as they relate to the presence of WNS at hibernacula near (<25 km) Fort Drum. A priori , we expected that overall activity for communal hibernating species would be less in years following WNS, and migratory bats or those hibernating bats that are less affected by WNS would show no response or a positive response, due to niche relaxation/competitive release. Our results indicated both an overall and seasonal decrease in activity for Myotis spp. post-WNS. For WNS-susceptible species, our results reflect the high level of mortality in regional winter hibernacula post-WNS and possibly variable reproductive effort and recruitment thereafter. Although migratory bats did show increases in post-WNS activity throughout the summer, we found little evidence that community displacement was occurring on a nightly level by any species. The continuous spread of WNS across North America has had strong negative effects on bat populations of affected species, and our research identifies how individual species (both impacted and non-impacted) respond to WNS.

New York↗

USGS2023

Nocturnal basking in freshwater turtles: A global assessment

Diurnal basking (“sunning”) is common in many ectotherms and is generally thought to be a behavioural mechanism for thermoregulation. Recent studies have reported the occurrence of nocturnal basking in a few distantly-related species of freshwater turtles, but the true extent of this behaviour is unknown, and it may be underreported due to sampling biases (e.g., not surveying for turtles at night). Therefore, we initiated a global, collaborative effort to systematically document and quantify basking activity (diurnal and nocturnal) across a wide range of freshwater turtle species and locations. We conducted camera trap or manual surveys in North America, the Caribbean, Europe, Asia, Africa, the Seychelles, and Australia. We collected 873,111 trail camera photographs (25,273 hrs of search effort) and obtained data on 29 freshwater turtle species from seven families. Nocturnal basking was documented in 13 species, representing six families (Chelidae, Emydidae , Geoemydidae, Kinosternidae, Pelomedusidae, and Trionychidae), including representatives in Central America, Trinidad and Tobago, Africa, the Seychelles, Asia, and Australia. Nocturnal basking was restricted to tropical and sub-tropical locations, suggesting that environmental temperature plays a role in this behaviour. However, the primary factors driving nocturnal basking are yet to be determined and may vary geographically and by species. The frequency and duration of nocturnal basking varied among species and seasons, but nocturnal basking events were often substantially longer than diurnal events. This is the first study to document a widespread occurrence of nocturnal basking, and our results suggest that nocturnal basking may be a common, although overlooked, aspect of many species’ ecology.

Global Ecology and Conservation↗